Effects of Maleated Hemp Seed Oil (MHO) on Mechanical Properties of Polylactic Acid Infilled Thermoplastic Starch

Polylactic acid (PLA) is one of the most widely used bioplastics due to its biodegradability and biocompatibility, but it also has defects such as hardness and brittleness, which limit its application. Blending thermoplastic starch (TPS) with PLA is an effective solution to the hardness and brittleness of PLA, but there is also the problem of poor PLA/TPS compatibility. In this case, a compatibilizer is usually used to improve the compatibility of the two components.
In this paper, maleic anhydride was used to modify hemp seed oil to obtain maleated hemp seed oil (MHO), which was used to improve the compatibility between PLA/TPS (80:20).

Figure 1 presents the mechanical properties of PLA/TPS with different percentages of MHO added. It can be seen that the Young's modulus and tensile strength of PLA/TPS decrease with the addition of MHO, while the elongation at break and Charpy impact strength both reach their maximum values when 7.5 parts of MHO are added, which are different from those without MHO. Compared with the PLA/TPS of 155% and 65% respectively. This shows that the addition of MHO can improve the compatibility of PLA/TPS, changing from rigidity to flexibility.

Figure 2 is the fracture morphology of PLA/TPS with different percentages of MHO added. The fracture in Figure 2 (a) is smooth, which is a typical brittle fracture; Figure 2 (b)-(d) shows that the spherical distribution of TPS in PLA gradually becomes uniform, indicating that the compatibility has been improved; Micropores appear in Figure 2(e), which is caused by the formation of droplets of excess MHO, which is easy to form defects.